Attempts have been made to develop low cost, simple lasers for use as light sources in laser display systems, biophotonics detection systems, and semiconductor micromachining systems. Passively-Q-switched lasers are attractive for these applications as they arc simple and low cost, yet produce powerful pulses of light that are immediately useful, or are well suited to converting to other wavelengths. Passively Q-switched lasers can produce pulses over a wide range of repetition frequencies and pulse energies, further enhancing their utility. However, most applications have not adapted the use of passive Q-switching. Acousto-optic Q-switching is much more prevalent due to its greater ability to produce strong pulses and its ability to produce these pulses in close synchronization with the other functions of the system. Acousto-optic Q-switching has become the standard, although it is a more complex and expensive technique than passive Q-switching. This expense and complexity has prevented the use of Q-switched lasers of any kind in many applications, particularly high volume, lower cost situations.
Although passive Q-switching is simpler and less expensive than acousto-optic Q-switching, passively Q-switched lasers are unable to deliver pulses in close synchronism with an externally-applied clock frequency. Although the pulse repetition frequency is proportional to the power with which the Q-switched laser is pumped, there is no direct way to synchronously control the pulse repetition frequency of a passively Q-switched laser. There is no equivalent of a trigger that can put out pulses on demand.
Should this deficiency be overcome, the PQSL would have application in tasks such as electronic trimming of integrated circuits and other micromachining. Through frequency conversion, the PQSL would become a good choice for fluorescence microscopy, flow cytometry, and other biophotonic applications. This inability to be synchronous, due to the free-running characteristic of PQSLs, has limited their use.
Thus, there is a need in the art, for a passive Q-switched laser control systems and methods that overcome the above disadvantages.